of Cold Neutron Source of Cold Neutron Source Myong-Seop KIM, - - PowerPoint PPT Presentation

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Myong-Seop KIM, Sung-Yul HWANG, Hoan-Sung JUNG and Kye-Hong LEE Korea Atomic Energy Research Institute 2005 TRTR-IGORR Meeting, 2005 TRTR-IGORR Meeting, Gaithersburg Gaithersburg, , September 12-16, 2005 September 12-16, 2005

Measurements of Nuclear Heating Rate Measurements of Nuclear Heating Rate and Neutron Flux in HANARO CN Hole and Neutron Flux in HANARO CN Hole for Designing the Moderator Cell for Designing the Moderator Cell

• f Cold Neutron Source
• f Cold Neutron Source

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Introduction-1

 Design of cold neutron source facility in HANARO : now in progress.  Heat removal capacity of moderator cell : essential information for source design.  Determination of nuclear heating rate at CN hole of HANARO. Determination of the capacity of refrigerator.

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Introduction-2

 Nuclear heating : nearly all the energy absorbed in a material placed in the radiation field of a research reactor appears in the form of heat.  Nuclear heating in research reactors : interactions with gamma-rays, fast neutrons and thermal neutrons.  Determination of nuclear heating rate by calorimetric dosimeter (calorimetry) : advantages for high-dose applications.  In this research,

• Designing and constructing a calorimeter,
• Measuring the nuclear heating rate at CN hole of

HANARO with it,

• Measuring the thermal neutron flux at CN hole.

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Concept of calorimeter operation

 In equilibrium condition of steady state, the power integrated over the volume of the sample, : sample and container temperatures, : heat transfer coefficient, : sample surface area, : thermal resistance.  If thermal resistance is known, the nuclear heating rate can be obtained by measuring the temperature difference in the steady state.

) (

e s

T T hs P − =

s h

e s T

T ,

hs / 1

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Experimental setup

Weight Sensor Sleeve

 Applicable for heating rate measurements in another vertical irradiation holes of HANARO.  Components

• a calorimeter sensor,
• an air containing

aluminum sleeve for fitting the sensor to the CN hole,

• aluminum weight,
• a lead wire assembly.

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Sensor part of calorimeter

Al sample Heater

TC1 TC2

Al pipe for neutron flux measurement AlN neutron detector for in-core testing

12 8 11 3 1.5 80

0.2 mm φ STS wire

 A cylindrical Al sample.  Al container.  Al pipe for the neutron flux measurement.  Two thermocouples.  Electric heater for a calibration.  Air gap.  Longitudinal center of Al sample is equal to the center of reactor core.  Calibration : a simulation of the heat transfer of the calorimeter

• ver the temperature range and

under the irradiation condition.

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Calibration experiments

 Installation of facility at CN hole of HANARO (zero reactor power).  Measurements of sample and container temperatures with the electric power supplied to the heater loaded in the sample.  The maximum sample temperature : 385 at 20 W. ℃  The change of container temperature : several . ℃

 whole trends of the temperature changes in the calibration experiment.  Temperature change : exponential growth function.

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Calibration curve

 Relationship between the power supplied to the heater and the temperature difference : not linear.  Convective and radiative heat transfers are increased in high sample temperature range.

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Measurements of nuclear heating rate and neutron flux

 Measurements of nuclear heating rates at the CN hole at three reactor powers of 1, 4 and 8 MW.

 Cobalt wire irradiations at the reactor powers of 1 and 8 MW for the neutron flux measurements.  Measurements of the activities of the withdrawn cobalt samples : HPGe detector system.  The diameter of the cobalt wire : 0.05 mm (negligible self- shielding effect).

HPGe Detector Preamp

Amp

Oscillo- scope Detector Bias Supply

PC

Analogue Digital Converter Multi- Channel Analyzer

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Measured nuclear heating rates-1

0.143±0.0041 5.618 137.062 177.220 40.158 8.48 0.018±0.0007 0.697 32.118 63.284 31.167 1.18 0.076±0.0023 3.000 85.540 122.592 37.051 4.20 19.411

Nuclear heating rate at sample [W] Sample temperature [℃] Container temperature [℃]

0.494 29.30 (30 MWth)

Heating rate per sample unit mass [W/g] Temperature difference [℃] Reactor power [MW]

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Heating rate/sample mass [W/g] Reactor power [MW]

Measured nuclear heating rates-2

Heating rate at 30 MW : 0.494 W/g

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Measured neutron flux

2.314 ×1013 8.602 ×1010 600 0.395 8.48 3.294 ×1012 1.224×1010 1800 0.252 1.18

Irradiation time [sec] Co-wire weight [mg]

7.450 ×1013 29.30 (30 MWth)

Neutron flux [n/cm2sec] Saturated activity per nuclei [Bq] Reactor power [MW]